The effectiveness of propagating optical energy through the atmosphere from a High-Energy Laser (HEL) source for long distances can be based on the ability to maintain maximum irradiance on a specified area at the target location. This propagation efficiency is degraded by many factors, including: molecular absorption and scattering, aerosol scattering and absorption, atmospheric turbulence, thermal blooming (from absorption and heating of the air), jitter of the optical axis, power and beam quality losses of the HEL source, and limits for any compensation technologies to correct for these phenomena. Adaptive optics processes can be used to correct and mitigate the degradation of propagation efficiency. Known Adaptive optics processes use a measurement of the optical aberrations along an optical path to generate a conjugate phase that is launched from the HEL source. As the HEL wavefront propagates through the turbulent atmosphere, the phase conjugation signal is “undone” by the turbulence and other aberrations, resulting in a correction to the HEL wavefront to provide a wavefront having flat phase front at the target and having high irradiance at the target.
Known adaptive optics elements in HEL systems employ components such as deformable mirrors that are shaped by actuators to generate a surface that modifies the wavefront phase of the laser source for producing a mathematical conjugate of the measured aberration along the propagation path in the atmosphere. These deformable mirrors and other components can be expensive, involve requirements for high level of optical cleanliness, and can be subject to optical and electrical damage. This can be particularly so for adaptive optics systems designed for high energy light beams. The elimination of these costly elements can provide significant cost savings, potentially better performance, improved system reliability and maintainability, and more compact, lightweight packaging. In addition, the limitations of the known adaptive optics designs in terms of spatial resolution, actuator/control loop bandwidth, and servo electronics prevent standard design approaches from compensating for fine-grained, high temporal frequency fluctuations along the optical path.
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